System for correcting sound records



Oct. 27, 1931. R. J. POMEROY 1528,940

SYSTEM FOR CORRECTING SOUND RECORDS 2 Sheets-Shee 1 Filed May 22, 1928 Inventor. A 0 J Pomem Oct. 27, 1931. R. J. POMEROY 1,328,940

SY STE" FOR CORRECTING SOUND RECORDS 2 Sheets-Shee 2 Fiied May 22. 1928,

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Patented Oct. 27, 1931 ROY .1. POMEROY, or HOLLYWOOD, CALIFORNIA I SYSTEM FOR CORRECTING SOUND RECORDS Application filed May 22, 1928.-

This invention relates generally to sound records,: and is particularly concerned with methods ofperfecting the reproduction of sound. The invention, in its broadest aspect,

is applicable to any type of sound-record containing representations of a sound Wave, and therefore may be adapted to either mechanical, photographic or other records.

Reference is here made to my ,c'opending 1 a JJlications filed on even date herewith enl.

titled System for correcting sound records, Serial No. 279,790, and Production of corrected sound-records, Serial No. 279,791, in which are disclosed variations and extensions of the invention as herein disclosed, the broad claims gene-ricto the'common general method being included within the present application. For thexpurpose of illustration, the invention is hereinafter particularly described and shown with reference to the photographic type of record. However, it will be understood thatthe invention is not intended to be Ill ' gible.

limited thereby, but is to be considered as applicable to any record of sound vibrations. Photographic sound records may, be of several types, and all such types are adaptable-to the invention. One such record, the one to which. I shall'have particular reference in the following specification, consists of a'shaded band of constant density, a variableor wavy outline representing the sound character and volume. Such records, and also the methods for their making and reproduction, are well known and need no particular description here.

In reproducing sounds from these records,

acertain objectionable distortion is always introduced within the various units involved, this effect being due mainly, however, to the speaker. Recording systems may be constructed in which'only a very slight distortion is introduced in making these records, and this may ordinarily be considered as. negli- The chief concern is therefore with the distortions of reproduction.

It is an object of this invention to provide a means of compensating these distortive effects so that a more perfect reproduction of the originalsound will beattainable.

. original sound record;

Serial No. 279,789.

1 Thisinvention provides'a method and system for making a distortion corrected record, and it does so byintroducing to the original record correction distortions that are compensatory of, or have a neutralizing effeet on, the distortions which are introduced by reproduction. In the procedure hereinafter described, this is done by recordin the distorted reproduced sound, and utilizing this distorted record to modifythe original record in such amanner that the distortive ellects oi the system are compensated. in the modified record, and perfect reproduction is thus obtainable.

H ow this is done will be better understood from the following detailed description of a typical means for carrying out the invention, reference for thepurpose being had to the accompanying drawings, in which:

igure 1 shows diagrammatically a system suitable for carrying out the invention;

Fig. 2 shows an original sound record represented as a positive upon a photographic film; V

Fig. 3 shows a photographic distortion record of sound as reproduced from the Fig. 4 shows a distortion correcting sound record; i k v 1 Fig. 5 shows an original sound record corrected fordistortion; I

Fig. 6 is a curve representing the relation between the outlines of the original andthe distortion records; and I Fig. 7 shows diagrammatically a varias tional system for carrying out theinvention.

The invention will first the assumption that no distortive effects are present in makingthe original sound record, or if actually present, are entirely negligible; distortion is thus exclusively the record within the reproducing system, and it will be shown how these effects are compensated. It will thereafter be pointed out that any smalldistortions arising in making thefilm, even though they may be negligible for practical purposes, will also be corrected within the system.

With reference" to the shows a photographic film be described with drawings, Fig.' 2 10 containing an I p original positive P0 of a sound record of constant density, the variable wavy outline 11 representing the sound character. An original positive photographic record, in the terminology herein employed, is the photographic record obtained by ordinary light printing-from the original negative record, not illustrated, obtained in originally recording the sound. A positive record is simply, in the usual sense, the reversal of a negative, or in other words is the record which would be obtained by ordinary light printingfrom a negative record. These terms when applied to the type of record here referred course merely relative, since either a positive or a negative may be used as the sound record, as is well known, and therefore the substitution of positives for negatives and negatives for positives throughout produces an equivalent method which falls properly within the scope of the claims using these terms. The sound record is illustrated upon the film in two sections, differing in that one is of a greater frequency than the other, but otherwise being identical and having corresponding parts indicated by like numerals. For L1 ie sake of -simplicity, the record of a continuous uniform sound is chosen for represenation in the drawings, but it will be understood that the various relations to be hereinafter pointed out apply in the same manner to a sound wave of a complex nature. The records are shown in somewhat enlarged proportions in order to clearly indicate their various existing relations.

The positive record P0 is run through the system of Fig. 1 which consists of photographic sound reproducing and photographic sound recording systems. The reproducing system must be the same system, or one havin g identical characteristics, as the one which is to be finally utilized in reproducing the sound. The recording system will preferably also be the same as was used in originally making the record, or one that introduces little or no distortion. With reference to Fig. 1 the film 10 containing the positive record P0 is shown traveling between an illuminant I and a photo-electric cell P. plate having a slit S1 is interposed between the illuminant and the photo-electric cell. Light rays from the illuminant I pass through the'slit S1, are modulated by the record upon the film, and affect the photoelectric cell P. Modulated current from the photo-electric cell P is conducted into the amplifier A1, and thence reproduced as sound by the speaker unit H, this sound having the distortions of the reproducing system. Amplifier A1, and other amplifiers to be mentioned later, may be any suitable electrical or vacuum tube amplifiers adapted to amplify an audio-frequency electrical current. i

A microphone M of the sound recording to areof.

system picks up the distorted sound, a sound current being conducted therefrom through the amplifier A2 to the glow tube Gr, before which travels a film 20. A plate having a slit S2 is interposed between the glow-tube and the film. The film 20 thus takes a photographic distortion sound record, indicated in the figure as a negative Nd, of the distorted sound reproduced from the positive record Po, the operation of the parts of the system being well. known and requiring no further description here. It. is only necessary here to note that the reproducing system I, S, P A1, H, is the same asthat which will be used in final reproduction, and that the recording system M, A2, G,.S2 is the. same as" the one initially used for making. original record P0 (or one introducing little or no distortion) so that the distortion record Nd with its sound wave line 21 is subs antially a reproduction of original record P 0 but with t e distortions of reproduction imposedupon it. While a negative record is illustrated as being obtained upon film 20, whether this record is actually a negative or a positive, within the meaning herein employed, that is, wi h relation to the positive input record Po,'depends upon various factors such as the polarity of photo-electric cell 1 and microphone M with respect to their amplifiers avoid confusion, it will hereinafter be assumed in all cases throughout the specification, however, unless otherwise stated, that the systems are so arranged that no reversals from a positive record representing current to a negative record representing current, or vice-versa, are obtained, or in other words that a negative photographic record is obtained by reproduction and recordation of the sound wave representation of a positive photographic record, and vice versa. It will be understood, however, that a number of variations of the method may be carried out, for instance, by arranging the system to give a positive distort-ion record from a positive orginal record, as mentioned above, and by varying the printing operations as hereinafter indicated and described; Such variations, of course, lie within the'scope of my invention. The negative record Nd contains all of the distortions introduced within the reproducing system, those arising within the recording system being considered as relatively so small as to warrant being neglected for the present. Negative record Nd is hereinafter referred to as a distortion record. and its outline as the distorted curve 21. This distorted curve 21 is shown superposed in dotted lines upon the positive record P0 in Fig. 2, and it will be seen that the distortion introduced in the reproducing system at any point in the record is represented by the difference in ordinates of the. curves 11 and 21. Q

In thisfsimple'case, the distortion may be represented, as in Fig. 6, by a sinewave, the

A1 and A2. To

for thls reason that 'nal record.

ordinates of which are obtaiined bysubtractingthe ordinates of the dlStOI'tGd'CllIVG 21 from those of the originalcurve 11. tically, the curves 11 and 21 willusuallybe complex, being the resultant waves the characteristics of and in any-specific case may depend upon the varying factors of sound character.

been illustrated in two sections of difierent requencles, one illustrating a case in which may be relatively minuswith respect to the origi- By a consideration of curves 11 and 21 of F ig; 2, it will be apparent that the action of he reproducing system has been to decrease the amplitude of vibration at the frequency of the first section of the record, and to increase the amplitude of vibration at the frenal record, and vice quency of the second. The positive record P0 is nowto be artificially modified by the relative addition of opacity at those points at which the distortion is at which the distorted traction of opacity at those points at which the distortion is relatively plus, or at which the distorted curve 21'rises above the original curve 11, the amount of this modification at any pointbeing always equal to the distortion atthat point.

that themodi fied recordis made relatively as much more opaque than the original record as the distortion record is less opaque than the origiversa, as the case may be.

If then this modified record is run through the same reproducing system, the distortions introduced by that'system will again be added and subtracted in the same sense orjdi-' rections as before; but now the reproducing system causes the sound wave of the modified record to be altered within the system to the shape and proportions of the original wave,

and distortionless audible reproduction of theoriginal sound wave is obtained.-

11, depending upon I curve 21 falls below b the original curve 11, and by the relative subslmple manner th of the original Po, and a positive record Pd of the distortion negative record N d, the numeralsll and 21 again representing the original and distorted curves respectively. As concern is to be merely with relative values, these'being represented for instance by the distance between the curves, or the difference of their ordinates, the entire areas of the origlnal sound records P0 and Nd need not api I 7 pear upon the film 30, and the films may therethe sound record has I be so positioned in of convenient width the record outlines 11 and 21.

I I then have upon film'30 a transparent correction band lined by the curves 1]. and 21. It will be apparent that if there were no distortions introduced within the system, curves 21 and 11 would be similar and the width of the band printing that a band in width by the diff the original and distorted curves '11 and 21 is obtained between T in an opaque field and out erence of ordinates of.

as they are shown in Fig. 2. These diflerences, which represent the distortions, are either positiveor negatlve, as the case may be, as indicated in Fig. 6; and the width of accordance with these values. The width, of the band C thus departs from the value which it would have if there were no distortions, by the amount of the distortions themselves.

A film 40, shown in Fig. 5, is then printed alongone edge with an opaque correction and C in duplication of the transparent correction band C, and with the original rec- P0 along the other, care being taken that t e two prints, the original record and the correction band, are accurately registered with each other.

I have thus added a band of opacity to I e original record, this band varying in Width with the'distortions; and the relation of these variations to the original record will now be pointed out. By a consideration of the characteristics of the opaque correction band C, and by a comparison of'this band with the original and distortion record outlines 11 and 21, as shown in Fig. 2, the following may be noted. At those points-of the original curve 11 at which the distorted curve 21 falls below that of the original curve. opacity has been added to the original record P0 in a greater amount than has been added at those points at which the distorted curve rises above that of the original curve. And, keeping in mind the "fact that these posalter the original recorc curve of Fig. 6, it

itive' and negative variations from a of constant width (which gives rise-to the varia tional addition of opacity just noted are equalin amount to themagnitu tortions, it will be apparent that I have relatively added opacity by the amount of the distortions where the opacity of the distortion record falls below the original record,-and relatively subtracted opacity by-the amount of the distortions where the opacity of .the distortion record rises above the original rec- 0rd. Another manner of stating this is that I have relatively added opacity to the original record by the amount of and negatively to the sense of the distortions.

While it is theoretically necessary only to the amount of and negatively to the sense of the distortions, thus applying corrections such as are indi cated, with proper regard to signs, by the is thought thatthe invention may most readily be practiced by the method out-lined above; that is, by the addition to the original record of an opaque band that varies in width with the distortions as above set forth, and thus relatively both adding and subtracting opacity in accordance with the invention. y

The result of running'the film with its altered sound record through the reproducing system will then be that the distortions inherently associated with the reproducing systern will act to correct the sound waves represented by this oppositely distorted record, changing them back to the original wave shape and proportions, and thus audible sound is reproduced without distortion.

It will now be shown that any small distortions which might be introduced inmaln ing the record will also be compensated for. These effects were neglected in the previous discussion, and legitimately so, for they may be made to be of inconsequential proportions. However, the inherent nature of the system takes care of them, whatever they may be.

From a consideration of the method and system hereinbefore set out, it will be apparent that the original positive record P0 will actually contain whatever distortions are introduced by the original recording system with whichit was made in the first place. And, further, the outline 21 of thedistortion record No will actually differv from outline 11 of the original record P0 by an amount which is equal to the resultant distortion introduced by both the reproducing system and the recording system. T he applied correction therefore'involves the distortions of both the reproducing and recording systerns. and compensates, therefore, not only for the distortions which will be introduced at any subsequent reproduction, but also compensates for the distortions introduced by the original recording system. Both the recording and reproducing'systems utilized to modde of the discarries at its ify the record must, ofcourse, be the same, or have identical characteristics, as the ones used in originally-recording and finally reproducing the sound. 1

It will now be shown how the distortion correcting record 30 or distortion correcting band C may be madewithout the necessity of first making the distortion negative Nd, the

positive Pd being originally recorded along with a previously prlnted negative N0, thus obtaining directly the correction band C. In order to carry this variation into effect, thefollowing consideration must be taken into account. It will be noted that the sound wave current obtained by reproduction as in Fig. 2 of the positive record P 0 represents a negative sound record, and with the ordinary photographic recording means, as indicated in the figure, a negative Nd is obtained. The present objective, however, positive Pd rather than the negative Nd and to obtain this positive directly by the operation of the system rather than by subsequent printing operations. This may be accomplished by substituting a negative N0 of the ayinal positive P0 in the system of Fig. 1, in which case a postive Pd obtained in place of the negative Nd; or positive Pd may be obtained from positive P0 by a system such illustrated in Fig. 7, in which system means 1 are provided for recording directly the positive Pd from the negative sound record representing current obtained by reproduction of P0. Thesystem as there shown is similar, in part, to that of Fig. 1, and similar parts are therefore indicated by like numerals. In this case, however, the output leads and 51 of amplifier A2 are in circuit with a photographic sound recording means adapted to reverse the sense of the sound wave representation before recording upon the film, this provision being made for the reason set out above. As atypical means of accomplishing this purpose,I show in circuit with the amplifier output leads 50 and erated shutter actuating means 52. This means may be any which will control theposition of a' light intercepting shutter in accordance with an electrical sound current, and is therefore conventionally illustrated. In the form shown in the drawings, the amplifier output leads 50 and 51 are connected to a coil 53' having a movable core 54:. Pivotally connected to the upper end of core 54 is a lever 55 which is fulcrumed at 56 and free end a'shutte'r 57 adapted to traverse the light slit 58. r

The traversing movement of'the shutter is con trolled by the sound current flowing in the coil 58, as will be understood' Light rays from a constant light source '59 are modulated by the shutter in accordance with the sound current, pass through the slit, and are recordedupon a traveling film 60 which has printed upon it a 'negativ'e record N0 of i the is to obtain a- 51 an electrically op-' 'nal'record P0 me and positioned The shutter is so car.-

from an original positive Po, as was previousby properly larity of the input to one of the amplifiers A1 or A2,"and in this case the usual g tube light valve is'used in place of the el'ectrically actuated shutter.

he invention has thus far been described ascorrecting or compensating the distortions occurring in the simple record-ation and reroduction of any typical sound record. The road invention, however, has numerous apglicatmns in furtherance of th s specific use.

casting. 1 For this purpose, sound would be broadcastfrom sound records'in which c ompensation has'heen' madefor the distortions introduced in their making and reproduction, and also for thedistortions introduced by the radio broadcasting set, andby the average radio receiving equipment.

While I have illustrated the invention with the aid of a constant density, varying outline photographic records, as involving the addition and subtraction of opac-- lty, and therefore any type of photographic sound record isre sponsive to the method. 1 In its broadest aspect, in whichis' embraced all orms of sound'records,

uced-in recording'and reproduction. q It will be understood that the method and system ashereinpresented are to be con-. sidered as merely illustrative ofand not re-. strictive upon; the invention considered in its roadest'sense, forvarious modifications of the methodandsystem may be made without departing 'frlornthe spirit and scope. oi the broader'claims appended hereto.

more, the method and system. as herein dis-V closed,v with its attendant .equlvalents, is but one of several means of reaching, the same general end, by 'the,same general principles ofprocedure; Other such means and systems are set out in'said-copending applications,

all within the generalbroad aspects of the v with respect" to the film that the record printedwith N pressed upon the leading ,to final audible reproduction of the changing the po'- I it will be apparent that the es invention which is both broadly and specifi cally claimed here. v

, claim:

opacity of the undistorted sound, to this record a band of opacity which varies from a band of constant width by the amount of and oppositely to the distortions imsound in the operations said photographic sound record.

2. he method of. making sound records that includes making an original "photographic sound record having a sound track area-of varying total opacity, making a photographic distortion sound record from and by reproduction of the original photographic sound record, and making a modifiedphotographic record by relatively altering the original record by the amount of andin a reverse sense to the distortion as indicated by the difference in total opacity at any point between the original and distortion records,

a manner that the distortions-are added reversely to the original i algebraiodifierence obtained by subtra ting the opacity of thedistortion record from the opacity of the original record at that point. 4. The method of making sound records that includes, making an original photographic sound record having a sound track area of varying total opacity, audibly reproducing the sound, the sound thus reproduced being distorted, making a photographic distortion record of the distorted sound, making a record of the distortions by combining an original photographic record and the record of distorted sound, and finally making a photographic record in such a manner that opacity is relatively added to the original record by the amount of and in a sense negative to the distortions of reproduction.

5. The method'of mak' that 1nclude s, making varying total opacity'reproducing sound from this positive. record, making a photo: graphic distortion negative record of the sound as reproduced, combining upon a film record nal positive in a manner a negative of the original positive record and a positive of the distortion negative record to produce a correction record representing the difierence of the last two records, and printing a negative of the correction record upon afilm having an original positive record in such a. manner that the distortions are added reversely to the original record.

6'. The method of making sound records that includes, making an original photographic sound record positive of the constant density, varying outline type, reproducing sound from said positive, making a distortion negative of the sound as reproduced and with the same type of record, printing side by side upon a film a negative of the original positive record and a positive of the distortion negative record, and rinting a negative of the record of said last mentioned film upon a film containing an original positive recort in such a manner that the distortions are added reversely to the original record. 7

7. The method of making sound records that includes, making an original photo graphic positive record of the audible sound. said record involving a sound track area of varying total opacity, audibly reproducing the sound, the sound thus reproduced being distorted, making a. photographic distortion positive record of the distorted sound, making a photographic modifying record by combining on a film the distortionpositive record with a negative of the original positive record in a mannerto provide a transparent corrective band which represents the reproductive distortions negatively, and combiningupon a film an originalpositive sound and an opaque duplicateof the corrective band in register with each otherin such a manner that the distortions-are added reversely to the original record.

8. The method of making sound records that includes, making an original photo.- graphic positive record of the audible sound, said record involving a sound track area of varying total opacity, audibly reproducing the sound, the sound thus reproduced being distorted, making aphotographic distortion negative record-of the distorted sound, making a photographic modifying record by combining on a film a positive of the distortion negative with a negative of the origito provide a transparent corrective band which represents the reproductive distortions negatively, and combining upon a film an original positive sound record and an opaque duplicate of the corrective band in register with each' other in such a-manner that the distortions are" added reversely to the original record.

9. A photographic sound record consisting of, an originalrecord'havin}: a sound track area of, varying total opacity, and a varying corrective band of opacity" which relatively alters the total opacity of the original sound in an opposite sense to the distortions intro duced in reproduction of the original record.

10. A photographic sound record consisting of, an original record having a sound track area of varying. total opacity, and a varying corrective band of opacity which relatively alters the total opacity of the original sound record by the amount of and in an opposite sense to the resultant distortions introduced in recording and reproducing the original record. I

11. A photographic sound record consisting of, an original record having a sound track area of varying total opacity, and a varying corrective band of opacity which relatively adds opacity to the original record by the amount of and in an opposite sense to the distortions introduced in reproduction of the original record.

12. The method of making sound records, that includes'making an original sound rec- 0rd, then reproducing said original sound record, obtaining from such reproduction a record of the distortions of reproduction and combining such record of: distortion reverse- 1y with the original to produce a distortion compensated record.

a 13. The, method of making sound records, that includes making an original photographic sound record, then reproducing said originali sound record, obtaining from; such reproduction a photographic-record of the distortions of reproduction and combining such record of distortion reversely with the original to produc'ea distortion compensated record.

14. The method of making soundrecords that comprises, making a constant density varying outline photographic record of the undistorted sound, and adding to this record a band of opacity which varies from a band of constant width by the amount of and-oppositely to the distortions impressed upon the sound in the operations leading to final audible reproduction of the said photographic sound record.

15. The method of makingsound records that includes,,makingan original constant density varying outline photographic sound record, audibly'reproducingthe sound, the sound thus reproduced being distorted,'making a photographic distortion record of the distorted sound, making a photographic modifying record-'ofthe distortions by com-. bining an original photographic record and the record of distorted sound, and finally making a modified record by combining an original photographic record with the moditying photographic record in such a manner that opacity is relatively added to the original record .bytheamount ofand in a record by the amount of and day of March, 1928.

sense negative to the distortions of reproductlon.

16. The method of making sound records I that includes, makin an original constant density varying outl1ne reproducing the sound, the sound thus reproduced being distorted,,making a photographic distortion positive record of the distorted sound, making ,a photographic modifying record by combining the distortion positive record with anegative of the original positive record in a manner to provide a transparent correctiveband which represents the reproductive distortions negatively, and combining upon aefilm an original positive sound record and an opaque duplicate of the corrective band in register with each other in such a manner that the distortions are added reversely to the original record.

17. A photographic sound record consisting of a constant density varying outline original record, and a varying outline corrective band of opacity which relatively alters the original record by the amount ofand in an opposite sense to the distortions in troduced in reproduction of the original record.

In witness that I claim the foregoing I have hereunto subscribed my'name this 24 ROY J. POMEROY, 

